package com.atguigu.binarysearchnorecursion;

public class BinarySearchNoRecur {

  public static void main(String[] args) {
    // 测试
    int[] arr = {1, 3, 8, 10, 11, 67, 100};
    int index = binarySearch(arr, 100);
    System.out.println("index=" + index); //
  }

  // 二分查找的非递归实现
  /**
   * @param arr 待查找的数组, arr是升序排序
   * @param target 需要查找的数
   * @return 返回对应下标，-1表示没有找到
   */
  public static int binarySearch(int[] arr, int target) {

    int left = 0;
    int right = arr.length - 1;
    while (left <= right) { // 说明继续查找
      int mid = (left + right) / 2;
      if (arr[mid] == target) {
        return mid;
      } else if (arr[mid] > target) {
        right = mid - 1; // 需要向左边查找
      } else {
        left = mid + 1; // 需要向右边查找
      }
    }
    return -1;
  }
}
